How Can I Merge Identical Cells Vertically in a WinForms DataGridView?

Vertically Merging Cells in a WinForms DataGridView

Challenge: You're working with a WinForms DataGridView, and need to visually merge identical cells vertically to improve data presentation.

Solution: This involves custom methods and event handling within your DataGridView.

Custom Functions:

First, create a function to compare cell values:

<code class="language-csharp">private bool AreCellsIdentical(int column, int row)
{
    // Compare the current cell's value with the cell above it.
    // Return true if they match, false otherwise.  Handle nulls appropriately.
}</code>

Event Handlers:

Next, use the CellPainting and CellFormatting events to control cell rendering:

CellPainting Event: This event allows you to modify the cell's appearance. Hide the bottom border of a cell if its value matches the cell above it.

<code class="language-csharp">private void dataGridView1_CellPainting(object sender, DataGridViewCellPaintingEventArgs e)
{
    // Check for identical cell values using AreCellsIdentical().
    // If identical, suppress the bottom border.
}</code>

CellFormatting Event: This event controls the cell's value display. Clear the value of a cell if it's identical to the cell above.

<code class="language-csharp">private void dataGridView1_CellFormatting(object sender, DataGridViewCellFormattingEventArgs e)
{
    // Check for identical cell values using AreCellsIdentical().
    // If identical, clear the cell's value (e.Value = null;).
}</code>

Additional Setup:

Disable automatic column generation to maintain control over styling:

<code class="language-csharp">dataGridView1.AutoGenerateColumns = false;</code>

Outcome:

Implementing these steps provides a visual effect of vertically merged cells, enhancing the clarity of your DataGridView.

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